Download Kidneys-Student Notes

Chapter 9
Excretion and the Interaction of
Systems
Goals for This Chapter
1. Identify the main structures and functions of the
human excretory system
2. Explain the function of the nephron
3. Describe the function of the kidney in excreting wastes
and expelling them into the environment
4. Describe how the kidneys maintain homeostasis with
respect to water and ions
5. Relate the design of dialysis technologies to the design
of the kidney
The Importance of Kidneys
• The liver removes an amine group from
proteins, forming ammonia
• ___________ is extremely toxic
• The liver then combines this ammonia with
carbon dioxide to form urea
• The kidneys then filter out the urea and uric
acid from the blood
Excretion of Wastes
• Excretion is the process of separating wastes
from the body fluids and eliminating them
• The respiratory system and the skin are both
involved in excretion
• However, the elimination of solid food residue
(feces) is not considered to be excretion
The Urinary System
• Renal arteries branch from the aorta and
enter the kidneys
• Waste is filtered from the blood in the kidneys
and sent to the bladder via _______
• The urinary sphincter at the base of the
bladder releases urine into the urethra, where
it leaves the body
The Urinary System
Bladder Volume
• ____ ml the bladder stretches and sends a
message to the brain indicating that it needs
to be emptied
• At ____ mL, a more urgent message is
produced
• At a volume of ____ mL, the voluntary control
of the bladder is lost, and it empties itself
The Kidney
• The kidney has three different structures
• An ______________, the cortex, encircles the
kidney
• The inner layer, the _______, is found beneath
the cortex
• The pelvis is a _____________ which joins the
kidney with the ureter
Nephrons
• The nephrons are the functional units of the
kidney
• Tiny __________ arterioles supply the
nephrons with blood
• These arterioles branch into a capillary bed
known as the glomerulus
• Blood leaves the glomerulus by the
_________ arteriole
• The glomerulus is surrounded by a _______like structure known as Bowman’s capsule
• Fluids to be processed into urine enter
Bowman’s capsule from the blood
• The capsule tapers to a thin tubule called the
________ tubule
• Urine travels through the loop of Henle and
into the distal tubule and into the collecting
ducts
The Nephron
• Identify the pathway
that blood moves
through the nephron
Formation of Urine
•
1.
2.
3.
Formation of urine involves three functions:
1. Filtration
• Blood moves into the ___________, which
acts as a high-pressure _____
• Dissolved solutes pass through the walls of the
glomerulus into Bowman’s capsule, creating a
_______
• Some things are too large to pass through the
membrane (_______ and ______ cells)
2. Reabsorption
• About ____ mL of fluid per minute is filtered
into the nephron
• Reabsorption is required otherwise you would
need to continually consume fluids to
maintain homeostasis
• Out of the 120 mL, _____ mL are reabsorbed
• This is accomplished by active and passive
transport
• Carrier molecules carry Na+ ions out of the
nephron into the blood, negative ions follow (Cland HCO3- )
• The concentrated solutes in the blood create an
osmotic pressure that pushes water back into the
blood
• Glucose and amino acids are also reabsorbed by
the blood by attaching themselves to carrier
molecules
• This also increases osmotic pressure into the
blood
3. Secretion
• Secretion is the movement of _______ from
the blood into the nephron
• Nitrogen wastes, excess hydrogen ions, and
mineral levels are balanced through secretion
• Secretion involves active transport, but
molecules are shuttled from the blood into
the nephron
Water Balance
• Increased water intake is adjusted for by
increasing urine output
• The kidneys rely on the nervous and
endocrine systems to help maintain a balance
of water
Regulating ADH
• _____ (antidiuretic hormone) regulates the
osmotic pressure in the kidneys to ________
water absorption
• If ADH is released, more __________ urine is
produced
• Cells in the hypothalamus get dehydrated and
shrink, (because of the solutes in the blood)
signaling the hypothalamus to release ADH
• Why do you feel thirsty?
• As you take in water, the solute levels in the
blood drop
• This reduces the osmotic pressure, allowing
fluids to move from the blood into the
_____________, releasing less ADH and
causing ____ water to be reabsorbed by the
nephrons
ADH and the Nephron
• ______ of the water filtered into the nephron
is reabsorbed in the ________ tubule
• ADH makes the upper part of the distal tubule
and collecting duct ________ to water
• This allows NaCl in the intercellular spaces to
create an osmotic pressure that draws water
from the tubule back into the blood
Kidneys and Blood Pressure
• Kidneys regulate blood pressure by regulating
blood volume
• Aldosterone acts on nephrons to
___________ Na+ ___________
• If there is a decrease in blood pressure,
aldosterone is produced, which increases Na+
absorption and therefore brings more water
into the blood, increasing its volume (and
therefore, pressure)
Kidneys and Blood pH
• The blood pH is maintained by acid-base
buffer systems
• The most important acid-base buffer system is
the following equation:
H+ + HCO3-  H2CO3  H2O + CO2
pH increases
pH decreases
• The kidneys help to maintain this balance by
balancing ____ and _____
• What happens if the blood is too acidic?
Diabetes Mellitus
• Diabetes mellitus is caused by inadequate
levels of ________
• Without insulin, _____________ levels rise
• The excess sugars remain in the nephron,
creating osmotic pressure that opposes the
osmotic pressure created by other solutes
• As a result, diabetes mellitus sufferers
produce excess urine which contains high
amounts of sugar
Diabetes Insipidus
• This occurs when ADH-producing cells of the
__________ are destroyed
• This causes a dramatic increase in urine
output (up to ___ L of urine per day!)
• People with this disease must drink huge
volumes of water to maintain fluid balance
Bright’s Disease (Nephritis)
• This collection of diseases is characterized by
_____________ of the nephrons
• ________ and other large molecules enter the
nephron via damaged blood vessels
• These molecules cannot be reabsorbed,
creating an osmotic pressure that pulls water
_____ the nephron, _________ urine
production
Dialysis
• If a kidney loses its function, then the patient
may be in danger of dying from uric acid
poisoning
• One solution for this condition is to perform
dialysis
• During dialysis treatment, a person’s blood is
filtered using a machine
Dialysis Machines (Hemodialysis)
• A dialysis machine consists of a long tube
made from a semipermeable membrane
immersed in a solution
• This solution contains the same ingredients as
clean blood plasma
• The patient’s blood (known as dialysate) is
passed through this tube and the wastes
diffuse into the surrounding solution
• Dialysis treatments take between 2 and 5 hours,
and may be repeated up to three times a week
• As well, patients must have a strictly regulated
diet to prevent excess levels of toxins to build up
in their systems
Peritoneal Dialysis
• Peritoneal dialysis uses the lining of the
intestines (the peritoneum) as the dialysis
membrane
• The dialysate is introduced into the abdominal
cavity, where the large surface area and the
rich supply of capillaries slowly filter the blood
Kidney Transplants
• One permanent solution to dialysis is to
replace the damaged kidney with a fully
functional one
• Kidney transplants often involve a close family
member donating one of their healthy kidneys
to the patient
• As a result, both the donor and recipient will
have one fully functional kidney
• However, because
both the donor and
recipient only have
one kidney, they
should closely
monitor their diet in
the future
• Kidneys can also be
obtained from
cadavers as long as
the organ donation
card had been filled
out
The Kidney-Coronary Connection
• Kidneys can fail due to high blood pressure
• If the blood vessels in the kidneys are
damaged due to high blood pressure, they
lose their ability to filter wastes effectively
• Unfortunately, the symptoms of high blood
pressure and kidney impairment to not appear
until the damage has already been done
Stones
• Kidney stones areKidney
collections
of
______________ from the blood
• These sharp stones become lodged in
the pelvis or the ureter, causing
severe pain
• Ultrasound can be used to break up
these stones so that they will be
passed in the urine (previously, only
surgery could remove the kidney
stones)